Conductivity of Water - was : [TCML] Running a TC in snow

["David Rieben" <drieben@xxxxxxxxxxx>]

Hi all,

I think we all agree that absolutley pure water is
indeed a good insulator and is sometimes used
for that very purpose. The trick is KEEPING it
that pure. It requires a constant deionization pro-
cess to keep water that pure, as it readily dissolves
many compounds and readily and quickly mobi-
lized electrons to create conductive ions.

During firefighter training, I was taught that it is
okay to attack an electrical fire with water IF
the fire stream is broken so that the current will
not have a steady path back to the nozzle through
the water stream. A fog stream, where the water
droplets are finely divided, is not considered to be
electrically conductive but a straight stream MUST
be shut on and off quickly as to not allow a com-
plete, unbroken conductive path between the
energized conductor(s) and the nozzle (and fire-
fighter!) Fog streams have a much better thermal
absortion than straight streams anyway due to the
greatly increased surface area of contact. Straight
streams are mostly used for greater reach and /or
penetration. Most live voltages encountered during
firefigthing activities are low voltage (< 600 volts)
and if high voltages are involved (substation or
transformer fire), the firefighters routinely wait
on the utility company to shut off the power before
attempting extinguishment with water. Of course,
the water for firefighting extinguishment ain't nothing
special, just from the city's water main (certainly
NOT distilled /deionized). It would be impractically
expensive to use hundreds or thousands of gallons
of distilled water for firefighting!

David Rieben


----- Original Message ----- 
From: "Phil Tuck" <follies@xxxxxxxxxxxx>
To: "'Tesla Coil Mailing List'" <tesla@xxxxxxxxxx>
Sent: Sunday, December 21, 2008 12:34 AM
Subject: RE: [TCML] Running a TC in snow


> Hello.
> I recently watched a TV program where power maintenance workers were
> cleaning insulators on  HV lines using a helicopter and a high pressure
> water cannon blasting distilled water. The commentator stressed the
> importance of the water being absolutely pure. I suppose otherwise it 
> would
> form a bridge no doubt between adjacent lines. So yes distilled water is
> non-conductive: something I never knew until seeing that program.
> So if the snow was formed from pure water, which is very unlikely, it may 
> be
> an insulator.
>
> As for testing that theory, I used to work in telecommunications and a 
> line
> could look great on a multi-meter but on a 5000 volt 'megger' it was a
> different story. These would even pick up damp on an insulated surface, 
> that
> was invisible to an ordinary meter and to the human eye.
> So if someone with a megger fancies taking a stroll in the
> snow...............
>
> I think of a Tesla coil to be a BIG 'megger', because all the snow on your
> body parts, wet feet, hands and head, all mixed with body salts, is most
> likely a great conductor. If you start slipping and sliding around,
> streamers and skin effects aside, the HV of the primary will certainly 
> warm
> up your cold hands and feet for you - far better than any cup of coffee
> would (or tea in the UK!).
>
> Phil
>
>
>
> -----Original Message-----
> From: Mike [mailto:megavolts61@xxxxxxxxx]
> Sent: 20 December 2008 00:57
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Running a TC in snow
>
> Hate to argue with you Dr. R,  but I just stuck my multimeter into a pile 
> of
> snow(got plenty of the white stuff around), and with the probe less that
> about half inch apart, I got a infinite resistance reading.  I would 
> venture
> to guess that as long as it is cold enough that the snow doesn't melt, it
> would actually not make a coil run significantly different than if in the
> same conditions without it snowing.   distilled water has a fairly high
> resistance as well...which snow would be very close to upon melting...I
> could see it shorting the spark gap if it were not enclosed somehow, but 
> if
> you set your coil up outdoors under a tarp until it is below freezing....I
> don't think much would ever happen bad."
> Mike
>
>
> > yes, bad idea.  Snow and water do not mix well with high
> > voltage.
> >
> > Dr. Resonance
>
>
>
>
>
>
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